This application is related to and claims priority from Japanese Patent Applications No. 2000-244614 filed on Aug. 11, 2000, and No. 2001-156033 filed on May 24, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a refrigerant cycle system having a hot-gas heater function using an evaporator as a radiator, and to a valve device used for the refrigerant cycle system. In the refrigerant cycle system, the hot-gas heater function is obtained by directly introducing gas refrigerant (hot gas) discharged from a compressor into the evaporator while bypassing a condenser.
2. Description of Related Art
U.S. Pat. No. 5,291,941 discloses a refrigerant cycle system having a heating function due to a hot-gas bypass. As shown in FIG. 12, a hot-gas bypass passage 118 is provided in this conventional system, and a heating decompression unit 117 and a heating solenoid valve 115A are provided in the hot-gas bypass passage 118. In addition, a cooling solenoid valve 115 is provided in a refrigerant passage through which refrigerant discharged from a compressor 110 flows into a condenser 119. Here, gas refrigerant discharged from the compressor 110 flows directly into an evaporator 128 through the hot-gas bypass passage 118 while bypassing the condenser 119 and the like. Further, the hot-gas bypass passage 118 and the refrigerant passage of the condenser 119 are selectively opened and closed by the cooling solenoid valve 115 and the heating solenoid valve 115A. Within an air-conditioning unit 126 disposed in a passenger compartment 125, a hot-water-type heating heater core 129 is disposed at a downstream air side of the evaporator 128. In a heating mode in winter, when a temperature of hot water circulating the heating heater core 129 is lower than a predetermined temperature, for example, when an engine 112 is started for warming up, high-temperature gas refrigerant (hot gas) discharged from the compressor 110 flows through the hot-gas bypass passage 118, and is directly introduced into the evaporator 128 after being decompressed by the heating decompression unit 117. Therefore, in the heating mode, heat is radiated from refrigerant to air in the evaporator 128, and the heating function for heating air can be obtained.
On the other hand, in a cooling mode, the high-temperature gas refrigerant discharged from the compressor 110 flows into the condenser 119 by closing the heating solenoid valve 115A and opening the cooling solenoid valve 115.
In the above-described system, however, both solenoid valves 115, 115A are used for switching refrigerant passages in the cooling mode and the heating mode. Further, a check valve 121 for preventing refrigerant in the hot-gas bypass passage 118 from flowing into the condenser 119 in the heating mode is provided separately from the solenoid valves 115, 115A. Accordingly, the number of components is increased, and production cost is increased in this system.
Further, a long piping is required for the hot-gas bypass passage 118 extending from an outlet of the heating solenoid valve 115A disposed around the compressor 110 in an engine compartment 124, to an inlet of the evaporator 128 in the passenger compartment 125. Therefore, mounting performance of the system on a vehicle is decreased.
In view of the foregoing problems, it is an object of the present invention to provide a refrigerant cycle system having a hot-gas heater function, which has a simple integrated structure of a valve device.
According to the present invention, in a refrigerant cycle system which switches an operation mode between a cooling mode where air is cooled by evaporating low-pressure refrigerant in an evaporator and a heating mode where air is heated in the evaporator by using gas refrigerant directly introduced from a compressor, a valve device includes a solenoid valve for opening and closing a refrigerant passage between a discharge side of the compressor and a condenser cooling and condensing refrigerant in the cooling mode, a differential pressure valve disposed to be opened by a pressure difference between the discharge side of the compressor and a side of the condenser, generated when the solenoid valve is closed, in such a manner that gas refrigerant discharged from the compressor is directly introduced into the evaporator when the differential pressure valve is opened, and a check valve disposed to prevent refrigerant at the discharge side of the compressor from flowing into the condenser when the differential pressure valve is opened. In the valve device, the solenoid valve, the differential pressure valve and the check valve are integrated by a housing member to construct an integrated structure. Accordingly, at least three kinds of valves, that is, the solenoid valve, the differential pressure valve and the check valve can be used as the integrated structure, thereby reducing an arrangement space of the valve device and the number of attachment steps. Further, the refrigerant cycle system operates by a combination of the one solenoid valve and the one differential pressure valve. Since the differential pressure valve can be made smaller, lighter and simpler than the solenoid valve in addition to the integration of three kinds of valves, the valve device can be produced in low cost while having a simple structure.
Furthermore, because the differential pressure valve is opened by the pressure difference between the discharge side of the compressor and the condenser, generated when the solenoid valve is closed, both the solenoid valve and the differential pressure valve are not closed at the same time. Therefore, it can prevent a refrigerant cycle circuit of the refrigerant cycle system from being closed when the compressor operates, and it can prevent the refrigerant cycle circuit from failing.
Preferably, in the valve device, the housing member is disposed to define a first refrigerant passage connected to the discharge side of the compressor, a second refrigerant passage connected to a refrigerant inlet side of the condenser, a third refrigerant passage connected to a refrigerant inlet side of the evaporator, and a fourth refrigerant passage connected to a refrigerant outlet side of the condenser. The solenoid valve is disposed to open and close a communication between the first and second refrigerant passages, and the differential pressure valve is disposed to open and close a communication between the first and third refrigerant passages. Further, the housing member is disposed to have therein a heating decompression means for decompressing gas refrigerant flowing from the first refrigerant passage to the third refrigerant passage when the differential pressure valve is opened, and to have therein a communication passage through which the fourth refrigerant passage communicates with a downstream refrigerant side of the heating decompression means. In addition, the check valve is provided in the communication passage. Accordingly, the fourth refrigerant passage connected to the outlet side of the condenser can communicate with the downstream refrigerant side of the heating decompression means through the communication passage in the housing member. That is, the downstream refrigerant side of the heating decompression means and the communication passage connected to the outlet side of the condenser can be joined to each other in the housing member. Therefore, it is possible to connect the third refrigerant passage of the housing member and the inlet side of the evaporator by only using a single low-pressure pipe.